The exchange of data, particularly audiovisual media, between devices that use or express that data, is commonplace. The data itself may be the product of a considerable investment of time and money. To protect this investment, distributors of such data often charge a price for the distribution of the data to those interested in obtaining it. However, if the channels over which the data is distributed are insecure, then others may receive the data without paying the price. This prevents those involved with the production or distribution of the data from recapturing the costs of their efforts.
In order to increase the security of the channels through which such data is transmitted, cryptographic systems may be employed. These cryptographic systems encrypt the data prior to its transmission over a communication stream to another device. Upon reaching the intended device, the data may be decrypted into its original, usable form. While encrypted, the data are not in a usable form. Those who do not possess the ability to decrypt the data are therefore unable to use the data. Therefore, cryptographic systems are designed to provide a level of assurance that the data can only be decrypted by those intended to have the ability to do so.
Various cryptographic systems exist. One such cryptographic system is High-bandwidth Digital Content Protection System (“HDCP”). The HDCP specification is well known in the art and therefore need not be described in detail herein. Briefly, HDCP is designed to protect video transmission between a Digital Visual Interface (“DVI”) transmitter and a DVI receiver. The DVI specification is well known in the art and therefore need not be described in detail herein. HDCP employs an authentication protocol through which a DVI transmitter verifies that a given DVI receiver is licensed to receive protected data. Then, when the legitimacy of the receiver is determined, encrypted data is transmitted between the two devices based on shared secrets established during the authentication protocol. Therefore, a transmission device may be seen as having an encryption unit (or layer) to encrypt the data, and a reception device may be seen as having a corresponding decryption unit (or layer) to decrypt that data.
Some cryptographic systems, such as HDCP, provide a certain level of cryptographic assurance, or security, at a cost that makes it financially feasible to use in many circumstances. For example, HDCP may utilize a key distribution cryptography system, which is generally known in the art to provide only a certain level of security, but at a lesser implementation cost. Other circumstances, however, may require a higher level of cryptographic assurance, or security, such as provided by a public key cryptographic, which is generally understood to provide a higher level of security, but at a higher implementation cost. Unfortunately, persons who have invested in a cryptography system such as a key distribution based HDCP system can currently only upgrade to a higher-level security system, such as a public key system, by abandoning the old system and entirely replacing it with a new system. This leads to undue implementation and maintenance costs.